Method for lifting flasks and molds

ABSTRACT

An arrangement is disclosed for improving the handling or stripping of the flasks or molds of the type which are used to cast large items such as cast metal plates or frames. A system is provided for lifting the flask or mold vertically from the pattern with assurance that each portion or part is moved at exactly the same rate and amount as every other part.

United States Patent Fismer [54] METHOD FOR LIFTING FLASKS AND MOLDS[72] Inventor: William L. Flsmer, 162 Franklin St.,

Verona, NJ. 07044 [22] Filed: May 15, 1969 [21] Appl. No.: 824,777

[52] US. Cl ..164/44, 164/213, 164/403,

254/93 L [51] Int. Cl. ..B22c 17/06 [58] Field of Search ..60/97 E, 97L; 164/44, 131,

[56] References Cited UNITED STATES PATENTS 2,484,646 10/ l 949Renkenberger 164/403 2,499,563 3/1950 'Bill ..60/97 P Feb. 22, 1972FOREIGN PATENTS OR APPLICATIONS 1,210,142 2/1966 Germany ..l64/40l451,555 9/1949 Italy ..164/227 Primary Examiner-J. Spencer OverholserAssistant Examiner-John E. Roethel Attorney-*Curtis, Morris & Safford IABSTRACT An arrangement is disclosed for improving the handling orstripping of the flasks or molds of the type which are used to castlarge items such as cast metal plates or frames. A system is providedfor lifting the flask or mold vertically from the pattern with assurancethat each portion or part is moved at exactly the same rate and amountas every other part.

4 Claims, 1 Drawing Figure METHOD FOR LIFTING FLASKS AND MOLDS Thisinvention relates to molding operations, and particularly hydrauliclifting mechanisms for raising the flask or mold upwardly from thepattern.

An object of this invention is to provide improved means for liftingmolds from patterns while forming molds for copes or drags. Anotherobject is to provide a simple and efficient arrangement for lifting withgreat precision any item such as a mold.,

ln casting items such as large plates or frames the top of the cavity isformed by the top mold or cope which is lifted away from the pattern atthe end of the mold-forming operation. Such items and the mold assemblyare so designed and constructed as to provide for the proper drawrelationship between the mold and the various portions of the pattern.When the dimensions of the top flask or mold are large it is difficultto insure that it will be lifted away from the pattern without tippingor canting. It is an object of the present invention to provide for thelifting of the top mold or flask with great precision and with assurancethat it is lifted at the same rate and amount throughout. These andother objects will be in part obvious and in part pointed out below.

The single FIGURE is a schematic representation of one embodiment oftheinvention.

Referring to the drawing, the flask or cope or drag ofa mold isrepresented at 2 and is square in horizontal section. Positioned at thefour corners of the flask are four hydraulic lifting units l2, l4, l6and 18 which are shown in alignment in the schematic drawing butactually are positioned so that their lift plates 4, 6, 8 and 10 arepositioned beneath lifting ledges at the four corners of the flask.Hydraulic lift unit 12 will be described and it is understood that theothers are identical with it. Unit 12 has a stationary cylinder 20, apiston 22, a piston rod 24 and a top cover 26 with a sealing boot 28around the piston rod. Extending from the bottom of cylinder is a liquidsupply line 30 which extends to the cylinder of a hydraulic operatingunit 34, and similar lines extend from the cylinders of units 14, 16 and18 respectively to the cylinders of operating units 36, 38 and 40 whichare identical with units 34. Each line 30 for the lifting units isconnected through a branch line 32 to a balancing valve 33 which will bedescribed more fully below.

Balancing valve 33 has a stationary valve body 90 and a valve rotor 92which may be turned by a handle 94. When the valve rotor is positionedas shown it closes the ends of branch lines 32. However, when the valvebody is turned 180 a cavity 96 in the side of the valve body ispositioned in alignment with branch lines 32 so as to interconnect them.Each of units 34, 36, 38 and 40 has a piston 42 which is connectedthrough a piston rod 44 to a plunger plate 46. Plunger plate 46 ismounted on the piston rod 48 to a main hydraulic unit 50 which has acylinder 52-and a piston 54 positioned within the cylinder and mountedupon the piston rod. Lines 56 and 58 are connected to the opposite endsof cylinder 52 so that piston 54 may be moved back and forth bysupplying liquid alternately to the opposite ends of the piston.

Lines 56 and 58 extend to a reversing valve 60 and extending from valve60 is a line 66 having a flow control valve 68 therein and extending tothe outlet ofa pump 70. Also extending from valve 60 is a liquiddischarge line 62 which extends to the top ofa liquid reservoir or sumptank 64. A branch of line 66 is also connected to a pair of dischargelines 74 and 76 extending to reservoir 64 and having pressure-controlrelief valves 78 and 80 therein, respectively. Valve 78 and 80 areoperative to bypass liquid from pump 70 back to reservoir 64 so as tolimit the maximum liquid pressure in line 66. As will be explained morefully below, valve 78 is adjusted to a lower maximum pressure than valve80 and valve 78 is rendered inoperative during the main portion of eachoperating cycle. Hence, valve 80 is always operative to provide amaximum limit on the pressure in line 66; whereas valve 78 acts onlywhen performing an operating function as is explained below.

Pump is driven by an electric motor 72 and when valve 60 is positionedas shown oil is delivered through line 66 and valve 68 to valve 60 andthence through line 56 to the head of cylinder 52. That drives piston 54to the left and causes liquid at the left of the piston to flow throughline 58, valve 60 and discharge line 62 to the liquid reservoir. Whenvalve 60 is turned 90 from the position shown the liquid under pressureflows through valve 68 and line 66 to valve 60 and thence through line58 into cylinder 52 to the left of piston 54. That moves piston 54 tothe right and drives liquid from the head of the piston through line 56,valve 60 and discharge line 62 to the liquid reservoir.

The system includes means not shown to maintain the cylinders of units34, 36, 38 and 40 and all of the lines 30 and 32 filled with liquid.Hence, with the parts positioned as shown the movement of piston 54 tothe left acts through plunger plate 46 and the piston rods 44 to movepistons 42 to the left in their cylinders. With branch lines 32 closedby balancing valve 33 unit 34 forces liquid into the bottom of-thecylinder of unit 12 and raises the piston therein so as to exert alifting force on plate 4. Similarly, each of units 36, 38 and 40 actstoexert a lifting force through its unit (14, 16 or 18) to exert a liftingforce on its lifting plate (6, 8 or 10). Hence with the operation justdescribed the supplying of liquid under pressure to the head of cylinder52 causes flask 2 to be raised. However, as has been pointed out above,it is important to insure that flask 2 is lifted the same amount and atthe same rate at all places; in this embodiment, at each of its corners.

in practice there is play in the operation of each of the units 12, 14,16 and 18 and that varies from unit to unit. For example, unit 12 maytake up the play and start lifting flask 2 prior to unit 14 at anadjacent corner or prior to unit 16 at the opposite corner. That mode ofoperation would be unsatisfactory and is avoided in accordance with thepresent invention. To accomplish that purpose there is an initialtightening" step which precedes the step of lifting the flask. Duringthat tightening step each of the units 12, 14, 16 and 18 is suppliedwith sufficient liquid under a controlled pressure which moves itspiston 22 upwardly so as to press its pressure plate (4, 6, 8 or 10)against its lifting ledge on the flask. The liquid pressure is not greatenough to produce any lifting movement on the flask so that each ofunits 12, 14, 16 and 18 is moved into lifting position but it cannotmove further upwardly.

That initial step is also carried on with valve rotor 92 turned to aposition with its cavity 96 interconnecting all of the branch lines 32.Hence, all of the units 34, 36, 38 and 40 act together in parallel tosupply liquid at a uniform pressure to all of the units 12, 14, 16 and18. Any differences in the operating relationship between one or anotherof one operating unit and its lifting unit (e.g., 34 and 12) and anotherare balanced out so that all of the operating units are exerting exactlythe same pressure and all of the lifting units are pressing theirlifting plates against the flask with the same force. Valve body 92 isthen turned to the position shown in the drawing so as to close theinterconnection between lines 32 and liquid at higher pressure issupplied through line 56 to unit 50 so that plunger plate 46 moves tothe left and each of the lifting units 34, 36, 38 and 40 then suppliedliquid to its lifting unit 12, 14, 16 M18 to lift the flask. Valve 68 isadjusted to control the rate at which liquid is supplied through line 66to line 56 and that controls the rate at which the flask is raised.However, each of the lifting units exerts the same lifting pressure atthe same rate as all the others and the flask is moved precisely thesame distance and at the same rate throughout.

It has been indicated above that valves 78 and are pressure-regulatingvalves and they are used to maintain the desired pressure of liquidsupplied through line 66. Pump 70 operates continuously and is adaptedto supply liquid at the pressure necessary to lift flask 2. However,valve 78 is adapted to limit the pressure of the liquid supplied in line66 to the value desired during the initial step of the lifting operationas described above. Hence, during that initial step when valve 33 isrendered operative and interconnects lines 32, relief valve 78 is alsorendered operative. Therefore, when all of the lifting units areproperly positioned during the initial step of a lifting operation, theoperating units can no longer move and that prevents piston 54 frommoving further in its lifting stroke. As a result, the flow through line56 stops and the pressure rises in line 66 to the value where valve 78opens and all of the liquid from pump 70 is returned through line 74 andvalve 78 to reservoir 64.

Valve 80 is a pressure-limiting switch which is effective when valve 78is not operating to limit the maximum oil pressure in line 66 and,therefore, the maximum pressure which is exerted at the lifting units.Hence, if for any reason flask 2 exerts abnormal resistance to thelifting movement, the pressures within the system rise and are limitedby the opening of the bypass valve 80. This valve 80 can also be used tolimit the lifting stroke by the arrival of the pistons 22 to the tops oftheir cylinders 20. Also, if there is malfunctioning in the system,valve 80 opens to prevent damage due to excessive pressures.

The return of the lifting components to their respective positions asshown is effected by returning valve 60 through 90 so that liquid underpressure is supplied from line 66 to line 58 into cylinder 52 at theleft of piston 54, and line 56 is connected to line 62 so as to permitthe liquid to flow from the right-hand side of the piston.

During the initial, step, as described above, with lines 32interconnected by the cavity 96, all variations in the amount of play inunits 12, l4, l6 and 18 and between their lifting plates and flask 2 aretaken up and there is an equalization between the liquid pressure units34, 36, 38 and 40. The equalizing overcomes any variation in the amountof liquid in the various cylinders which would cause an unbalance in thesubsequent lifting action. A stable condition is then reached in thisinitial step wherein pump 70 maintains the constant pressure determinedby valve 78 and all of the lifting plates are held against theirrespective ledges on flask 2 with the same pressure.

Hence, when valve 33 is turned to disconnect lines 32 and valve 78 isrendered inoperative by manual or automatic means, there is an immediateincrease in the pressure in line 66. That causes liquid to flow throughline 56 into cylinder 52 so as to move piston 54 to the left. That rateof movement is controlled by the adjustment of valve 68. The movement ofpiston 54 causes a corresponding movement of each of the pistons 42 and,the liquid not being compressible, there is a corresponding liftingmovement by each of the pistons 22. Hence. the lifting action isimmediate and uniform and the rate of lifting may be increased ordecreased by adjusting valve 68.

As indicated above, the flask is lowered into place by the reverseaction, and during the lifting and lowering, valve provides control toinsure against excessive pressure conditions.

It is thus seen that the operation is simple and dependable and thatflask 2 is moved with great precision at all times and that the aboveand other desirable objects are accomplished. It is understood thatmodifications in the construction and mode of operation may be madewithin the scope of the claims.

What is claimed is:

1. In the method of separating a mold and its pattern with the aid of aplurality of hydraulic lifting units having separate liquid supplies,the steps of, performing an initial step of providing engagement withsaid units at a plurality of zones with a predetermined lifting forcefrom a single source by interconnecting the supplies of liquid to saidlifting units and limiting the predetermined force by controlling theliquid pressure, after said engagements are made, disconnecting theinterconnection of the supplies of liquid to said lifting units and thenincreasing the lifting force at each of said zones with a total forcesufficient to perform the separating by increasing the liquid pressureapplied simultaneously and independently to said lifting units throughsaid supplies.

2. The method as described in claim 1 wherein the fluid pressure exertedin said initial step and said force increasin step 18 created by aplurality of independent units correspon ing in number to said liftingunits and connected respectively therewith and wherein said independentunits are operated simultaneously.

3. The method of separating a mold part and its pattern with the aid ofa plurality of hydraulic lifting units having separate liquid suppliescomprising, the steps of initially interconnecting said liquid supplies,pressurizing said separate liquid supplies from a single source toengage said mold part at a plurality of locations with each of saidlifting units at a predetermined lifting force, thereafter,disconnecting the interconnection between said liquid supplies andincreasing the pressure in said supplies applied by said single sourceto apply a total lifting force at said locations through said liftingunits sufficient to separate said mold part from said pattern.

4. The method as defined in claim 3 including the steps of limiting thepressure in said liquid supplies when producing said predeterminedlifting force and limiting the pressure in said liquid supplies whenproducing said total lifting force.

1. In the method of separating a mold and its pattern with the aid of aplurality of hydraulic lifting units having separate liquid supplies,the steps of, performing an initial step of providing engagement withsaid units at a plurality of zones with a predetermined lifting forcefrom a single source by interconnecting the supplies of liquid to saidlifting units and limiting the predetermined force by controlling theliquid pressure, after said engagements are made, disconnecting theinterconnection of the supplies of liquid to said lifting units and thenincreasing the lifting force at each of said zones with a total forcesufficient to perform the separating by increasing the liquid pressureapplied simultaneously and independently to said lifting units throughsaid supplies.
 2. The method as described in claim 1 wherein the fluidpressure exerted in said initial step and said force increasing step iscreated by a plurality of independent units corresponding in number tosaid lifting units and connected respectively therewith and wherein saidindependent units are operated simultaneously.
 3. The method ofseparating a mold part and its pattern with the aid of a plurality ofhydraulic lifting units having separate liquid supplies comprising, thesteps of initially interconnecting said liquid supplies, pressurizingsaid separate liquid supplies from a single source to engage said moldpart at a plurality of locations with each of said lifting units at apredetermined lifting force, thereafter, disconnecting theinterconnection between said liquid supplies and increasing the pressurein said supplies applied by said single source to apply a total liftingforce at said locations through said lifting units sufficient toseparate said mold part from said pattern.
 4. The method as defined inclaim 3 including the steps of limiting the pressure in said liquidsupplies when producing said predetermined lifting force and limitingthe pressure in said liquid supplies when producing said total liftingforce.